A large security presence remains in place in flashpoint areas of Belfast for the main day of the Protestant Orange Order marching season.

There were several protests as contentious parades passed nationalist areas without incident on Friday morning.

Tens of thousands of people are taking part in celebrations by the loyal order which commemorates William of Orange's 1690 Battle of the Boyne victory over Catholic King James II.

Meanwhile, dissident republicans opposed to the Northern Ireland peace process have been blamed for leaving a large firebomb close to the route of the main parade in Belfast.

A controlled explosion was carried out on the van

In Ardoyne in north Belfast, Orange lodges and bandsmen made their way past a crowd of about 200 nationalist protesters who were chanting: "End sectarian marches."

Police Superintendent David Boultwood said he was pleased there was no violence.

"When you can bring a parade past of this size and there's no violent disorder, that is good for us, good for the area and good for society as a whole," he said.

Police have called for the same restraint when the marchers make their way back later on Friday.

'Riot planned'

Hundreds of police and soldiers are in place at Ardoyne shops, the scene of serious clashes on 12 July last year, when Orangemen made their way back to north Belfast.

Meanwhile, police have recovered a weapons cache containing more than 80 spiked missiles and several crates of bottles they believe were to be used as petrol bombs.

They were hidden in the roofs of premises in Ardoyne and the police said they believed they were to be rained down onto police and civilians in the street below.

In Ballymena, County Antrim, the police were attacked by a group of about 200 people protesting against an Orange parade in the town.

The protesters, who had gathered in the Dunclug estate, threw bricks, bottles and fireworks.

On the parade's return, petrol bombs and bricks were thrown at police by a group of more than 50 nationalists.

On Thursday night, the police recovered 23 petrol and acid bombs and a tin of petrol in the Dunclug area.

Earlier on Thursday, Assistant Chief Constable Alan McQuillan said he had information that republicans were planning to riot at Ardoyne.

Sinn Fein's Gerry Kelly and local police chief supervise Ardoyne protest

He appealed to Sinn Fein leaders to hold a peaceful and legitimate protest.

But Sinn Fein North Belfast assembly member Gerry Kelly said there were no plans by republicans to start trouble.

"What I have said to the residents here who are organising this protest is that there is a trap being set, by Alan McQuillan in particular.

"If he has all the evidence then let him produce it," said Mr Kelly.

Security sources have said they believe dissident republicans left a large firebomb close to the route of the main parade in Belfast.

Army explosives experts blew up a van containing a detonator and a large amount of petrol in the early hours of Friday.

Two controlled explosions were carried out following a telephone warning to police about the van in Little Donegall Street just after midnight.

Meanwhile, police said a suspicious object was discovered in an overflow field at a Twelfth demonstration in Dundrum in County Down.

The area was evacuated and Army bomb experts later declared the object an elaborate hoax.